Depends on the library, and perhaps on when you ask. The Cambridge Public Library web site now says they require a "current local address", so the homeless may

Depends on the library, and perhaps on when you ask. The Cambridge Public Library web site now says they require a "current local address", so the homeless may be out of luck. But they used to require only that you be able to sign your name. (This was advertised with posters featuring a very dejected looking cat.)